The invention relates to a vessel of thermoplastic material having a rolling ring projecting in axial prolongation of the cylindrical portion of the shell near the head, wherein the adjoining shell region from the bottom of the groove between ring and shell makes a conical transition into the head.
Conventionally, such vessels are equipped with cross-sectionally massive carrying and transport rings located in the neighborhood of the associated end surfaces, the rings having a horizontal and a vertical bearing surface for the arms of a vessel-handling lifter.
As a rule, these vessels are drums manufactured in their entirety by a blowing operation, the carrying and transport rings being formed in one piece with the shell in the process. However, there are other known vessels in which the tubular portion of the shell and the end portions are produced separately. The injection-molded heads with carrying and transport rings in place are welded to the tubular body of the vessel in an additional operation.
Because the carrying and transport rings are much endangered, owing to their comparatively small shell thickness, in event of oblique impact of a full vessel falling from some height, the position of the rings must be preceded by a so-called crumple zone in which the main energy of impact will be absorbed. This is done by arranging the rings at an interval beyond the head and/or bottom edges of the vessel. The shell regions extending beyond the ring groove rise conically towards the centerline of the vessel.
In oblique or perpendicular impacts of the falling vessel, the elastic end regions lying inside the rings undergo deformation before the rings are reached. Owing to the comparatively short distance of the rings from the head and/or bottom of the vessel, the operator rolling the vessel obliquely can grasp the rings with the hand, so that an extremely convenient handling results.
In oblique rolling of the full vessel, the edge of the head is pressed in flat by the weight of the vessel, with an undesirable wobbling action as the vessel is rolled. By bracing the carrying and transport ring in question against the head, the deformation of the head edge may be partly cushioned, thus mitigating the unwanted wobbling action.
Nevertheless there is still a marked impediment to the rolling of the vessel on the bottom edge. Furthermore, the edge region at the transition of the shell of the vessel into the head is comparatively thin, and may be overstrained in rough handling, especially in oblique rolling by hand. Besides, the danger of accident when tilting and rolling the vessel is heightened by the erect rolling ring, which may come down on the operator's foot.